[Coco] Nitros9 on a CC3 512k

[Gene Heskett]

On Monday 01 March 2010, Joel Ewy wrote:
>George Ramsower wrote:
>> Finally I get around to play with Nitros9, build a boot disk on my XP
>> box using Cocodisk from nos96809l2v030208coco3_80d.dsk and it has a
>> problem.
>> First, I used cocodisk to format the 720K 3.5" disk with 80 track, two
>> sided. Then did the "Write to disk" to do this.
>> The coco does boot and gets as far as the startup file and hangs.
>> Rebooting with a working OS9 disk and looking at the Nitros9 disk
>> reveals that the root directory appears to be intact but I cannot list
>> the startup file or peer into the cmds directory. Error 247.
>> I tried formatting a floppy on the coco and trying again but, with the
>> same result.
>
>George,
>
>I also use 720K 3.5" disks and have had similar issues with NitrOS-9.  I
>would suggest that you start out with the default disk image size, (40t,
>ds) for your first stab at booting NitrOS-9, and then make a proper 80t
>disk from within NitrOS-9.
>
>The problem I've had is with the DNS (density) flag in the disk
>descriptor.  It used to specify the Tracks Per Inch (as well as
>single/double density).  I think it may have been redefined.

The only thing I'm aware of as re-defined is the typ byte, this was at one 
point set to a value that indicates its an os9 format disk, and this is in 
the os9 manual.  If a $20 its a 5.25" floppy, and much later, if a $21, its a 
3.5" floppy.  We didn't have any of those smaller critters 25 years ago.

DNS gets confusing because in 5.25" disks ONLY when os9 was new, they tossed 
an extra bit in to define whether it was a 48 tpi format, or a 96 tpi format.  
This was done probably 20 years ago with the idea  that if the descriptor 
said it was a 96 tpi diskette, but ioman and rbf found a disk in the drive 
which claimed it was a 48 tpi disk, they could then double step the drive and 
read the wider tracks it had.  Where that item stubbed its toe badly, was in 
not making that 40 track disk in an 80 track drive, read only, because a 
write attempt wrecked the disk due to the new write not being as wide a track 
as the old one, and that made it so the wider heads in the 40 track  drive 
could only read garbage as some of the track was new, and some was old.

This change in the dns usage I believe took place with the level2 release, or 
very shortly after, but I don't have a handy book to swear on.
 
>All my old
>disks were 80T, 2S, 135TPI (3.5") with the DNS bits set accordingly.

Which for those s/b $01, there is not a 3.5" drive with other than 135 tpi 
track spacing.  The $03 belongs _only_ on a 720k, 96 tpi drive.  160k ss and 
360 ds disks should all remain at $01 for dns.

>The default device descriptors in NitrOS-9 are set to [whatever the TPI
>is for 5.25" drives].  Just setting them to 80 tracks with dmode doesn't
>work right.  It can see the root directory, but can't read anything else
>on the disk. 

Because its seeing a dns=01 disk, in a 96 tpi drive and trying to double step 
the drive, thinking its a 48 tpi 360k disk.

>Seems a lot like what has been happening to you.  I've
>given up dmode-ing the NitrOS-9 descriptors for 135TPI  and just leave
>DNS at the default, re-writing my old disks to match the new usage of DNS.
>
>So my suggestion is to make a 40 track boot disk (so you waste half the
>disk -- you can reformat it later) and then when you boot, dmode the
>device descriptors for 80T.  Make a new boot disk with these descriptors
>and see if you have better luck.
>
>JCE
>
>> I would offer more info but don't what to tell you. Ask me questions
>> and I will begin the discovery process as to why I'm getting this
>> problem.
>>
>> Thanks,
>>
>> George
>
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>


-- 
Cheers, Gene
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